[espadrine]

A subtle constraint to optimize is hardware cost.

I assume Disney chose to separate the constraints by going with simple hardware shapes, yielding a predictable cost and an easy construction. A good hardware optimizer would also need to engineer assembly, which seems nontrivial.

Software costs of optimizing motion for existing hardware are more predictable (~19 minutes of an i7-7700 w/ 32GB, per second of animation).

That being said, they acknowledge in their paper that they could optimize certain properties of the robot, like rod size or joint position.